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The following was received from the licensee via email: Medical Event on a Prostate HDR (high dose rate brachytherapy) Fraction #2. The patient was previously treated to Fraction #1 2 weeks earlier without any issue.

A patient was under spinal anesthesia for a treatment to the prostate to a prescribed dose of 13.5 Gy. The plan called for 19 interstitial catheters to the 30 cc prostate gland. The V100 of the prostate was expected to be 99.75% (100% dose of 13.5 Gy covered 99.75% of the prostate volume). All coverage and critical organ sparing criteria were met and physician approved the plan.

However during treatment and after completion of 9 catheters the treatment console reported an error (and subsequently retracted the source after 2 dwell positions were treated of the 10th catheter). The error code 9 message was source has moved from dwell position and a reset of the treatment console was required.

(The medical physicist) went inside the treatment room with the survey meter to ensure the source indeed retracted and transfer tube and applicator appropriately connected. Which they were. Attempts were made to continue with the treatment as the error code direction was cancel the error and try again.

However, the afterloader would not resume treatment and the treatment console reported an another error code 117 error during check out-drive in channel (driving out the check cable).

Several attempts were made with help of Elekta field service and phone support to troubleshoot the issue as the message on the treatment console with these errors is that if the problem persists, contact your local Elekta service representative. Troubleshooting continued afterwards with the field service engineer coming on site. We were later informed by the engineer that parts had to be ordered to resolve the issue and that they would arrive early the next morning.

The procedure was eventually halted due to the service issue and patient was sent to recovery and family informed.

(The licensee is) now assessing what dose was delivered.

The total treatment time called for 386.6 s. However, only 158.5 s was treated. On the treatment planning system using the catheters and dwell positions and time of 158.5 s the v100 to the prostate is showing as 12.52% (100% of the dose of 13.5 Gy covered 12.52% of the prostate volume) of the partially treated procedure. There was no excessive dose anywhere i.e. to critical structures, just lack thereof to the intended treatment volume of the prostate. The dosimetrist is working with the plan to put on dose points near treated catheters to provide us further details.

(The licensee) wanted to take the appropriate direction going forward in regards to documentation, reporting and planning for treatment for the patient on a subsequent date. The machine issue initially occurred at approximately (1430 EDT on 3/16/16). Service on the unit is ongoing so exact details of the repair are not yet available. Remaining prostate patients scheduled for this week been rescheduled for a later date. A Medical Event may indicate potential problems in a medical facility's use of radioactive materials. It does not necessarily result in harm to the patient.